US2022247177A1PendingUtilityA1
Photovoltaic Solar Inverter with an AC Grid Filter Without Inductance
Assignee: POWER ELECTRONICS ESPANA S LPriority: Jan 27, 2021Filed: Jan 26, 2022Published: Aug 4, 2022
Est. expiryJan 27, 2041(~14.5 yrs left)· nominal 20-yr term from priority
Inventors:David Salvo LilloAbelardo Salvo LilloJosué Juan AguilarJosé Luis Camps SorianoEusebio Rodrigo Mañez
H02J 2101/24H02M 1/126H02J 3/38H02M 5/12H02J 3/381H02M 7/44H02J 3/01H02J 2300/24Y02E10/56
35
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Claims
Abstract
The present disclosure provides a photovoltaic solar inverter with an AC grid filter without inductance connectable to the AC grid. The inverter comprises: a power module for converting a DC input voltage into a three-phase AC output voltage; a three-phase AC/AC transformer for adapting the three-phase AC output voltage of the power module to the three-phase AC voltage of the AC grid, which has an inductance “L2”. The three-phase AC/AC transformer comprises a winding on the grid side with an equivalent inductance “L1”; a capacitor “C”, connected to the winding of the grid side of the three-phase AC/AC transformer. The equivalent inductance “L1” of the AC/AC transformer, the capacitor “C” and the inductance “L2” of the AC grid form a high frequency “LCL” filter, eliminating the inductances provided only for forming the LCL filter. The disclosure also provides an AC grid filter without inductance with an “LLCL” typology.
Claims
exact text as granted — not AI-modified1 . A photovoltaic solar inverter with an alternating current (AC) grid filter without inductance, wherein the photovoltaic solar inverter is connectable to the AC grid;
wherein the inverter comprises: at least one power module for converting a direct current (DC) input voltage into a three-phase AC output voltage; a three-phase AC/AC transformer for adapting the three-phase AC output voltage of the at least one power module to the three-phase AC voltage of the AC grid, which has an inductance, referred to as L 2 ; wherein the three-phase AC/AC transformer comprises: at least one winding on a low voltage side connected to the at least one power module; at least one winding on a grid side connectable in series with the AC grid; wherein the at least one winding on the low voltage side connected to the at least one power module together with the at least one winding on the grid side have an equivalent inductance, referred to as L 1 ; a capacitor, referred to as C, connected to the winding of the grid side of the three-phase AC/AC transformer; wherein the equivalent inductance, referred to as L 1 , of the AC/AC transformer, the capacitor, referred to as C, and the inductance, referred to as L 2 , of the AC grid form a high frequency inductance-capacitance-inductance (LCL) filter, such that the values of the equivalent inductance, referred to as L 1 , and of the capacitor, referred to as C, are calculated based on a frequency response of the LCL filter according to the following expressions:
L
1
=
X
cc
·
V
n
2
2
π
f
n
·
S
n
and
C
=
L
1
+
L
2
L
1
·
L
2
·
(
2
π
f
res
)
2
wherein:
X CC : is an equivalent impedance of a plurality of windings of the three-phase AC/AC transformer;
S n : is a nominal power of the three-phase AC/AC transformer;
V n : is a nominal voltage of the three-phase AC/AC transformer on the low voltage side;
f n : is a working frequency;
f res : is a resonant frequency of the LCL filter; and
L 2 : is an inductance of the AC grid which varies according to a Short Circuit Ratio (SCR) according to the following expression:
L
2
=
V
n
2
2
π
f
n
·
SCR
·
S
n
.
2 . The photovoltaic solar inverter with the AC grid filter without inductance according to claim 1 , wherein the photovoltaic solar inverter further comprises a number, n, of power modules each connected to a respective winding on the low voltage side of the three-phase AC/AC transformer, such that the equivalent inductance, referred to as L 1 , is calculated by means of:
L
1
=
(
x
+
(
1
-
x
)
n
N
)
X
cc
·
V
n
2
2
π
f
n
·
S
n
wherein:
x: is a proportion of impedance of the grid side;
N: is a number of windings of a low working side; and
n: is a total number of windings of the low voltage side.
3 . The photovoltaic solar inverter with the AC grid filter without inductance according to claim 2 , wherein the photovoltaic solar inverter comprises a single DC power BUS for powering the number, n, of power modules, and wherein the single DC BUS is connectable to at least one DC power source.
4 . The photovoltaic solar inverter with the AC grid filter without inductance according to claim 2 , wherein the photovoltaic solar inverter comprises one DC power BUS for each of the number, n, of power modules, such that each of the number, n, of power modules is connectable to a respective DC power source.
5 . A photovoltaic solar inverter with an AC grid filter without inductance, wherein the photovoltaic solar inverter is connectable to the AC grid;
the photovoltaic solar inverter comprising: at least one power module for converting a DC input voltage into a three-phase AC output voltage; a three-phase AC/AC transformer for adapting the three-phase AC output voltage of the power module to the three-phase AC voltage of the AC grid, which has an inductance, referred to as L p ;
wherein the three-phase AC/AC transformer comprises:
at least one winding on a first low voltage side connected to the at least one power module and with an equivalent inductance, referred to as L 1 ;
at least one winding on a second low voltage side connected to a capacitor, referred to as C, and with an inductance, referred to as L c ;
at least one winding on a grid side connectable in series with the AC grid, wherein the at least one winding on the grid side has an equivalent inductance, referred to as L M ; and
the capacitor, referred to as C; wherein the equivalent inductance, referred to as L 1 , of the AC/AC transformer, the inductance, referred to as L c , the capacitor, referred to as C, and an inductance, referred to as L 2 , resulting from adding the inductance, referred to as L p , and the equivalent inductance referred to as L M , form a high frequency filter with LLCL typology, such that the values of the equivalent inductance, referred to as L 1 , and of the capacitor, referred to as C, are calculated based on the frequency response of the LLCL filter according to the following expressions:
L
1
=
(
1
-
x
)
X
cc
·
V
n
2
2
π
f
n
·
S
n
;
C
=
L
1
+
L
2
(
L
1
L
2
+
L
c
(
L
1
+
L
2
)
)
·
(
2
π
f
res
)
2
;
L
cv
=
1
C
·
(
2
π
f
res
)
2
;
wherein:
X CC is a configurable element based on a frequency response needed for the LLCL filter;
x: is a proportion of impedance of a medium side;
S n : is a nominal power of the three-phase AC/AC transformer;
V n : is a nominal voltage of the three-phase AC/AC transformer on a low side;
f n : is a working frequency of the low side;
f res : is a resonant frequency of the LLCL filter;
and knowing that:
L 2 =L M +L P , wherein:
L
m
=
(
x
)
X
cc
·
V
n
2
2
π
f
n
·
S
n
;
L P : is an inductance of the AC grid which varies according to a Short Circuit Ratio “SCR” according to the following expression:
L
P
=
V
n
2
2
π
f
n
·
SCR
·
S
n
.
6 . The photovoltaic solar inverter with the AC grid filter without inductance according to claim 5 , wherein the photovoltaic solar inverter further comprises a number, n, of power modules each connected to a respective winding on the first low voltage side of the three-phase AC/AC transformer, such that the equivalent inductance, referred to as L 1 , is calculated by means of:
L
1
=
(
(
1
-
x
)
·
n
N
)
X
cc
·
V
n
2
2
π
f
n
·
S
n
wherein:
x: is a proportion of an impedance of a medium side;
N: is a number of windings of a low working side; and
n: is a total number of windings of the first low voltage side.
7 . The photovoltaic solar inverter with the AC grid filter without inductance according to claim 6 , wherein the photovoltaic solar inverter comprises a single DC power BUS for powering the number, n, of power modules, and wherein the single DC BUS is connectable to at least one DC power source.
8 . The photovoltaic solar inverter with the AC grid filter without inductance according to claim 6 , wherein the photovoltaic solar inverter comprises one DC power BUS for each of the number, n, of power modules, such that each of the number, n, of power modules is connectable to a respective DC power source.Cited by (0)
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